79 evinrude 100 hp idle way to fast

[jesballs57]

hey guys<br /><br /> my rude is idling at 2600 rpm.with timing set a 4 btdc.also the throttle roller is off the cam so the throttle plates are closed ,i visually checked the plates to make sure.some how there to much air /fuel mixture getting in .the low speed jets are not adjustable .the only way i can get the rpm down is by retarding the timing to about 8 atdc with causes the idle to be rough and plugs to get wet.the flywheel key is ok so timing is correct.any ideas guys? .by the way the number stamped in to the carb is 323302 any one know if this is the part # of the carb and if it is the right carb for my engine?

 

[rickdb1boat]

Re: 79 evinrude 100 hp idle way to fast

Have you checked for vacuum leaks around the carb bases? Spray some carb cleaner anywhere there might be a leak and see what happens. Check all the hoses, too. Did this just start or has it been this way for awhile? Motor new to you??

 

[jesballs57]

Re: 79 evinrude 100 hp idle way to fast

yeah i just bought it 2 months ago . runs perfect in high rpm.but the idle was rough so i put plugs in and replaced a coil that was bad.also changed thermostats. idle improved but was still rough and wetting plugs thats when i checked timing and run in to this . RB ill check for leaks tonite let you know<br /><br />jesballs57

 

[walleyehed]

Re: 79 evinrude 100 hp idle way to fast

Rick, any chance the timing mark is off and may be advanced too far????? I know the book says 4 BTDC, but I haven't seen very many very close to that, but that could be my altitude difference as well....Just a thought. <br /><br />EDIT: just re-read post....timming should be ATDC at IDLE, not BTDC.....am I thinking right here???<br />I've got an '81 OMC V4 book here at the house, and it says 4 Degs. BTDC is the point the cam follower makes contact with throttle linkage, so Idle timing should be less...like maybe 2-4 degs ATDC, or where Idle is about 700-750 with back pressure.

 

[rickdb1boat]

Re: 79 evinrude 100 hp idle way to fast

Ken, My book shows 4-6 degrees BTDC throttle pick-up (idle) 750 RPM's in the water in gear. 28 BTDC Full Throttle. I know what you're saying that it should be a bit less before it contacts the cam follower, but I think he has that right or at least close enough. I don't think a degree or two would make the idle soar like it is. Now if it's set ATDC, then that would be a problem. jesballs57, Make sure you have the timing set to 2 degrees BTDC at idle. If I understand what you're saying, it idled rough, but somewhat in the normal range, and then you adjusted the timing and it started the high reving? Is this correct or did it always idle real high? Are you sure when it's running, that the timer base is returning ALL the way to it's stop at idle? Sometimes they stick. Don't spray anything under the flywheel to "Loosen" it up. Let us know more info...<br /><br />EDIT: Do have an idle stop screw on there. Have you tryed backing that off. Just a thought, as you never know. Some do, some rely on the timing.

 

[jesballs57]

Re: 79 evinrude 100 hp idle way to fast

rb and walleyehed .yeah it did idle rough at about 800-900 rpm and die sometimes.about the timeing lever it does go all the way back ,but i do notice that its slow to catch up when you start to move the lever.hey is the throttle cam suppose to be in contact with the throttle roller or is there a gap before the cam pushes the the roller?if there is a gap then that would make sence why i cant get it to be a 4-6 btdc at slow idle.i guess the rpm increase from idle in gear to when cam hits the rollers is all timing advance ...do i have this correct? if this is correct im i chasing my tail . im to expect a rough idle ?. the reason im so concerned about the idle when in gear, is becuase i do a lot of trolling and would like it to idle a lot smoother , other than that my OB runns strong.

 

[walleyehed]

Re: 79 evinrude 100 hp idle way to fast

In neutral, the cam SHOULD NOT touch the roller....you may need to do a link-n-sync, which will require a manual, but is not hard to do if you follow the instructions properly.<br />Not knowing your plug conditions, I would recommend a set of 4 Champion QL82C plugs be installed-gapped at .040 for your application of trolling.<br />Rick may be correct with a possible intake issue (leak).<br />The timing arm has a spring behind it, and if dirt, grime or lack of lube is the case, the arm (pointing straight up) needs to be removed and cleaned as well as the nylon bushings. I have seen these get so dirty the return spring is not strong enough to return timing to idle position, although I've never seen one over about 1500-1700 RPM .......<br />Hang tight, Rick may have some other suggestions.<br />jes, another item you may want to consider when we figure this out, is installing a set of Boyesen reeds....best money you'll ever spend on an OMC V4 that sees alot of trolling speeds

 

[jesballs57]

Re: 79 evinrude 100 hp idle way to fast

hey wallyeyehed.<br />funny you say that i was just about to post about boysen reeds.do they really improve the idle that much? i searched the forum and all i found about boysen was guys more intrested in the top end they give you.i also looked on the boysen website they said it would improve the idle for that trolling speed.if thats the case ill buy some with my next pay check.<br /><br />jesballs

 

[walleyehed]

Re: 79 evinrude 100 hp idle way to fast

My Idle RPM on my 115 was about 700-750 before...with Boyesen reeds it's rock solid at 500 RPM.<br />The only thing I would mention is FOLLOW THE INSTALATION INSTRUCTIONS....the idle circut MUST be richened for these Reeds to work properly and last for a long time.